Spark plug construction



Mmh s. 1951' SPARK PLUG CONSTRUCTION Original Filed Oct. 1, 1947 H. R. FEIcHTER, 2,543,961

4 Shoots-Sheet 2 R99 l Harold R cil 'er @61M Ai; tornexjs Minn 6,1-,195'1 original Filed od. 1, 1947 H. n. rslcrq'n-:R

SPARK PLUG CONSTRUCTION 4 Shouts-Shoot 3 Attornegs H. R. Palm-ITER SPARK rwc cons'mumou Mach 6, 1951 original Filed oct. 1,1947

4V Sheath-Sheet 4 Attornegs Patented Mar. 6, 19751 2,543,961 srsax PLUG coNsraUc'rroN Harold R. Feichter, Canton, Ohio, asslgnor to United States Quarry Tile Company, Canton, Ohio, a corporation of Delaware Original application October 1, 1947, Serial No. 777,350, now Patent No. 2,478,259, dated August 9, 1949. Divided and this application February, 26, 1949, Serial No. 78,617

The invention relates to spark plug construction and to spark plugs for use in internal combustion engines for automobiles. aircraft, or wherever it is desired to ignite a combustible the present invention include freedom from gas leakage, freedom from rapid deterioration of the 3 Claims. (Cl. 12S-489) electrodes of the spark plug, convenient replaceability of the ground electrode. an arrangement of the reduced number of parts permitting broad scope in the design as to the size and shape of mixture, and this application is a division of my l the parts of the spark plug, a relative arrangeapplication, Serial No. 777,350. filed October l, ment of the size and shape of the parts of the 1947, issued August 9, 1949 as U. S. Letters Patent spark plug whereby there may be a greatly in- No. 2,478,259. This application contains subcreased length of the electrical leakage path beject matter that is relatedtomy copending applitween the central electrode of the plug and cation 78,618, filed at even date herewith. which ground. without increasing the overall length of is also a divisional application of my application the plug as compared with conventional practice. 777,350. f A further property of one form of the improved In a usual spark plug there are included a spark plug of the present invention in addition multiplicity of parts some of which are metal to the foregoing is the maintaining of a constant and which require a relatively large number of position of the lower end of the central electrode, manufacturing operations for the production of and the transfer of heat by convection through the separate parts and their assembly. circulation of a conducting liquid as well as by its In a usual spark plug there is included a metal own conduction, from the tip of the insulator or ground shell in which a tubular insulator is inelectrode to other portions and surfaces of the serted, and the tubular insulator has a bore exinsulator. tending entirely through the insulator, and a rod The foregoing and other objects are attained electrode is located in and extends through the by the spark plug construction, parts, combinabore of the insulator. tions. and sub-combinations, which comprise the At the lower end of the metal ground shell there present invention, the nature of which is set is welded or otherwise secured a ground elecforth in the following general statement, and trode.'and the lower end of the central rod elecpreferred embodiments of which together with trode is spaced from the ground electrode. It their mode of use are set forth by way of example is necessary to provide a gas sealing cement in the following description, and which are parbetween the rod electrode and the bore of the ticularly and distinctly pointed out and set forth insulator and it is also necessary to provide a in the appended claims forming partllereofgas tight seal between the insulator and the The nature of one preferred embodiment of the shell. e improved spark ,plug of the present invention In other words a usual spark plug includes a may be stated in general terms as including an multiplicity of parts which make the cost of nslllatOI body preferably of tired ceramic maproduction relatively expensive, the assembly of terial, the insulator body having formed therein the parts -being complicated and difllcult to cona well with an open upper end and the insulator trol to provide for a uniform finished product bOdyincluding a bottom wall extending across which does not deteriorate in usethe lower end of the well.' Electrode material is The objects of the present invention include located in the well, and the insulator body inthe provision ofanmproved spark plug construc- 40 eludeS a lower end having formed thereon eX- tion which is inherently adapted for a long ternal threads adapted for being screwed into period of use and which requires less metal than an internally threaded Opening in the Wall 0f a a usual spark plug construction, metal having combustion chamber such as the combustion become scarce as compared with ceramic machamber of Aan internal combustion engine. A terial, and in which there is a reduction in the replaceable metal ground electrode is provided on number of parts required to produce the imthe lower end of the insulator body adjacent the proved spark plug on the one hand, and which bottom wall of the well. provides the spark plug with substantially im- By way of example, a number of embodiments proved properties as compared with present spark of the improved spark plug construction of the plugs on the other hand. One of the more impresent invention are illustrated in the accomportant of these improved properties is the mini- =panying drawings forming part hereof, in which mizing of the necessity of replacing the spark Figure l is a longitudinal axial sectional view plug at intervals as frequently as has been necesof a first preferred embodiment of improved sary prior to the present improvements. spark plug hereof;

The properties of the improved spark plugs of u Fig. la is a similar view of the insulator body shown in Fig. 1, before assembly in the complete spark plus;

Pig. 2 is a similar view of a second embodiment of the improved spark plug construction hereof: Fig. 3 is a similar view of a third embodiment of the improved spark plug construction hereof; Fig. 4 is a similar view of a fourth embodiment of the improved spark plug construction hereof; Fig. 5 is a. similar view of a fifth embodiment of the improved spark plug construction hereof;

Figs. 6, '1, and 8 are views similar to Fig. la, showing modified forms of insulator bodies for the improved spark plugs hereof;

Fig. 9 is a fragmentary view similar to Fig. 1, showing a modifled form of ground electrode;

Fig. 10 is a view similar to Fig. l of a sixth embodimentof the improved spark plug construction hereof;

Fig. 11 is a view similar to Fig. 1 of a seventh embodiment of the improved spark plug construction hereof;

Fig. 12 is a bottom plan view of the spark plug construction of Fig. 10 looking in the direction of the arrows |2-I2-, Fig. 10;

Fig. 13 is a transverse cross section of the spark plug construction of Fig. 10 as on the line II-i3, Fig. 10;

Fig. 14 is a view similar to Fig. 1 of an eighth embodiment of the improved spark plug construction hereof;

Fig. 15 is a similar view of a ninth embodiment of the improved spark plug construction hereof; and

Fig. 16 is a similar view of a tenth embodiment of the improved spark -plug construction hereof.

Similar numerals refer to similar parts throughout the several views.

'I'he first preferred embodiment of the improved spark plug hereof is illustrated in Fig. 1 and is indicated generally by ID and includes an insulator body II preferably made of fired ceramic material, preferably having a high alumina content of upwards of 92 per cent, and also other ingredients, such as set forth in any of my U. S. Letters Patents No. 2,413,441, No. 2,414,367, No. 2,414,368, and No. 2,414,369.

The insulator body Il is shown in Fig. 1a before assembly in the complete spark plug III, and

' the insulator body II has formed therein a well I2 with an open upper end I3, and the insulator body II furthermore includes a bottom wall I4 extending across the lower end of the well I2.

The insulator body II is elongated, and the well I2 extends longitudinally coaxially with the longitudinal axis I5 of the insulator body I I. Metal electrode material is located in the well I2 which may be as shown in Fig. l a rod I6 of metal such as steel. The upper end Il of the well I2 may be enlarged and lprovided with internal threads, and the metal electrode rod I6 may have an enlarged head I8 which is externally threaded and screwed in the internally threaded enlarged upper end I'I of the well I2. The bottom Wall I4 is preferably thinner than the surrounding walls of the insulator body, and in itself seals the lower end of the well I2, and covers the lower end of the electrode rod I6 therein. The bottom Wall I4 preferably has a thickness between the limits of 5 thousandths and 125 thousandths of an inch. In addition, when desirable, the electrode rod I6 may be sealed in the well I2 in a usual manner as by ceramic cement.

The insulator body II has a reduced lower end indicated generally by I9 which includes an intermediate externally threaded portion 20 and a still smaller externally threaded extremity 2i.

The spark plug Il furthermore includes a replaceable ground electrode indicated generally by 22 which is made of metal such as steel or other hard metallic substance, and which includes an internally and externally threaded ferrule portion 2l whose internal threads are screwed on the externally threaded extremity 2i of the insulator body II, and the external threads of the ferrule 23 match the externally threaded portion 2l of the insulator body Il. The replaceable ground electrode 22 furthermore includes one or more electrode tips or points 24 made of nickel or like material and extending inwardly from the ferrule portion 23. I'he insulator body II furthermore includes a larger upper portion 2l and an annular shoulder 2l between the inner end of the threaded portion 2O and the larger upper portions 25, which has a larger transverse cross section than the transverse cross section at any place of the reduced lower end Il.

A metal combustion chamber wall 21 which may be a wall of a combustion chamber of an internal combustion engine has formed therein an internally threaded opening 2l in which are screwed the externally threaded lower end portion 2l of the insulator body II and the externally threaded ferrule portion 2l of the replaceable ground electrode 22.

In using the spark plug Il the central rod electrode I6 and the grounding metal combustion chamber wall 2l are connected in a usual ignition circuit which applies a potential to the central electrode rod I8, and from the lower end thereof contacting the well bottom wall I4 potential is applied to the bottom wall I4 until its charge is sufficient to cause a spark between the bottom wall I4 and the electrode tips 24.

In the improved spark plug Il the upper portion 25 of the insulator body Il may have any desired form and dimensions which are not subject to the form and dimensional limitations of a usual spark plug where the ground shell must be crimped over or otherwise fastened to an enlargement on the usual insulator body.

In the improved spark plug Il there is freedom from gas leakage by reason of the location of the central electrode I6 in the well I2, the solid bottom wall I4 of insulating material extending across the lower end of the well I2. Thus protecting the central electrode I8 prevents rapid deterioration of the lower end of the electrode Il. When the electrode tips of the ground electrode 22 become burnt oil' too much, a replacement ground electrode 22 may be conveniently and easily applied to the insulator body II. It is also to be noted that the length of the upper portion 25 of the insulator body I I is substantial whereby there is a greatly increased length of the electrical leakage path between the upper head Il of the central electrode IB and the grounding combustion chamber wall 21, this increased length of the electrical leakage path being effected without increasing the overall length of the plug as compared with conventional practice in spark plug construction where ground shells are used which extend a considerable distance above the combustion chamber wall in which the spark plug is mounted.

In Fig. 2 there is shown a second embodiment of the improved spark plug hereof indicated generally by I I0 and which is generally similar to the spark plug III, but in the spark plug lil the lnsulator body I I I has a bore I I2 extending entirely through the body, and a center electrode III loyamasar cated in the bore I I2 has its lower end protruding below the lower end of the insulator Vbody I I I. In the spark plug IISv there is also a replaceable ground electrode |22. The spark plug IIII has all the advantages of the spark plug Il with the exception of lacking a central electrode in a well.

In Fig. 3 there is shown a generally conventional spark plug indicated generally by 2I0 including a ground shell 23S at the lower end of which there is screw connected a replaceable ground electrode 222 which constitutes one of the improvements oi.' the present invention. The ground shell 23S has mounted thereinin a usual manner an insulator 2li in the central bore 2 I2 oi.' which there is sealed a central electrode 2IS in the usual manner.

In Fig. 4 there i3 shown a spark plug indicated generally by SIS which is of generally conventional construction including a ground shell SSII mounting an insulator body SI I which is modified from conventional construction by including a well SI2 having a bottom wall SII extending across the lower end of the well SI2, this being one of the improvements oi the present invention. There is located in the well SI2 a central electrode SIS.

In Fig. 5 there is shown a spark plug indicated generally by I I Il which is of modied conventional construction and includes a ground shell ISII. One of the improved removable ground electrodes of the present invention indicated generally by I22 is screw connected to the lower end oi.' the ground shell, and the ground shell mounts an insulator body III which is formed to include another of the improvements oi the present invention, namely a central well II2 having a bottom wall III extending across its lower end. A central electrode IIS is located in the well II2.

In Fig. 6 there is shown a modified insulator body indicator generally by SII which is generally similar to the insulator body I I, the insulator body SII having formed therein a central well SI2 having an open upper end SIS and a bottom wall SII extending across the lower end oi' the well SI2. Diiering from the solid bottom wall II of the insulator body II, the bottom wall SII has a microscopic hole SII-I formed therethrough by being punctured by a high tension electrical discharge passed therethrough by placing the wall SII between electrodes of an electric circuit in which there is a suilicient potential ditl'erence between the electrodes to eect the puncturing. In Fig. 6, the microscopic hole SII-I is ncessarily magnified.

For properly locating the hole SII-I, the top face of the bottom wall SII slopes to a central point SI I-2 which insures that the puncturing high tension electrical discharge will pass through the wall SII at the central point SII-2, the wall S I I being thinnest at that point.

In Fig. 7 there is shown another modified insulator body indicated generally by SI I which is also generally similar to the insulator body II, the insulator body SII having formed therein a central well SI2 having an open upper end SIS and a bottom wall SII extending across the lower end of the well S I 2. The bottom wall II oi.' the insulator body I I is formed entirely of insulation material, preferably tired ceramic material. The bottom wall SII diii'ers from this in that the bottom wall SII has one or more iine metallic wires such as platinum extending therethrough, these wires being inserted in the bottom wall before the firing is eiIected, the iiring serving to seal the wires in the bottom wall.

'IS place if the lower tip of the central electrode rod In F18. 8 there is shown a modified insulator body indicated generally .by 1II which is again generally similar to the insulator body I I, the insulator body 'II I having formed therein a central well 'II2 having an open upper end lll and a bottom wall III extending across the lower end of the well- II2. Instead of being of insulation material as is the solid bottom wall II of the insulator II, the bottom wall III includes a portion or is entirely made, as shown in the drawing, of conducting material, such as a combination of ceramic material and a metallic powder such s iron, nickel, chromium, or tungsten, sintered together.

The insulator bodies SI I, SII, and 'III each includes a diiierent means whereby a reduced potential diierence is required to effect the passage of an electrical discharge or current through their respective bottom walls SII, SII, and III, as compared with the potential difference required to effect the passage of a discharge through the solid bottom wall II of insulation material of the insulator body II, where all of the bottom walls have the same thickness.

In Fig. 9 there is shown a spark plug indicated generally by SIS which is generally similar to the spark plug III. but in the spark plug SIS the ground electrode S22 is formed by sprayed metal on the reduced lower end SIS of the insulator body SII.

It should also be noted that the replaceable ground electrode 22 on the insulator body II as shown and preferably is screw connected with the insulator body I I. In addition to being merely screwed on the insulator body II, the replaceable ground electrode 22 may be thermally sweated thereon.

In Figs. 10, 12, and 13 there is shown a spark plug indicated generally by S IS which is generally similar to the spark plug II with the exception oi' the construction and arrangement of thewell and central electrode. The spark plug SIII includes an insulator body SII having formed therein a central well SI2 having an open upper end SIS and a bottom wall SII extending across the lower end oi' the well SI2. The well SI2 has an increased diameter as compared with the diameter o the iuavell I2 of the insulator body I I of the spark p ug I In the lower end of the well SI2 there is located a body of conducting liquid preferably liquid metal SIS--I which may be mercury or a lower melting alloy oi.' bismuth, tin, lead, and antimony, or similar material. There is also located in the well SI2 a metal electrode rod SIS, the lower end o1' which extends into the body of liquid metal SIS-I, andthe metal electrode rod SIS has an enlarged head SIS which is externally threaded and screwed in the internally threaded enlarged upper end SI1 of the well SI2. A body of cement SSI seals the upper portions of the electrode rod SIS between the body of liquid metal SIS-I and the head SIS.

In the spark plug SIS the lower body o1' liquid metal SIS-I and the electrode rod SIS whose lower end is immersed in the body of liquid metal SIS-I constitute a. composite central electrode in which the lower end of the body of liquid metal SIS-I always rests upon the upper face of the well bottom wall SII. In other words the position of the lower end of the composite central electrode of the spark plug SIII always remains constant, where as disintegration of the lower tip of the central electrode rod SIS may take 7 III extends to the top surface of the well bottom wall 9M, and no body'of liquid metal lil-i is used. The body of liquid metal III-I ilows into any void produced in it on top of the well bottom wall lil.

Moreover, inthe operation of an internal combustion engine, for example, in which the spark plug 9 I 0 is in use, the hot gases in the combustion chamber served by the spark plug IIC heats the lower end of the spark plug III and the body of liquid metal BIB-I therein causing circulation of the liquid metal SIB-I, whereby there is a transfer of heat from the lower end 9|! of the insulator body 9H to upper portions and surfaces of the insulator body SII, this transfer of heet being effected by convection ot the body of circulating liquid metal 9I6-I, as well as by its own conduction.

In Fig. 11 there is shown a spark plug indicated generally by Ill-I whichis generally similar to the spark plug SIU and includes an insulator body leii having formed therein a central well III! having an open upper end IIII, and the insulator body IDII has a lower end IUI which has formed therein a bore IIII2-I which has a diameter reduced from that of the well IN2. An intermediate electrode shank IMO-2 is located and sealed in the bore IIiII--I and has on its upper end an enlarged head MIB-2 which nts and seals the lower end of the bore II I2. A body of conducting liquid IBIS-I is located in the lower end of the well IIJI2 and rests upon the top of the enlarged head lele-3 on the intermediate electrode shank Init- 2. A metal electrode rod itil is located in the well IIII2 and has its lower end immersed in the body of conducting liquid IMI-I, and a body of cement IIIII seals the upper portions of the electrode rod Il I 6.

In Fig. 14 there is shown a spark plug indicated generally by IIIO which is generally similar to the spark plug 9 I Il. The spark plug I I Il includes an insulator body IIII having formed therein a central well II I2 having an open upper end II I2 and a bottom wall I III extending across the lower end of the well I I I2. 'I'he insulator body lIiI has a reduced lower end II Il having a bottom face III9-I, and the well bottom wall lill is spaced above the bottom face I I il-I In the lower end I I I9 of the insulator body II I I there is formed an internally threaded socket I I IS-J in which is screwed an externally threaded intermediate electrode I I Il-2. The wall I I Il may be provided, if desired, with one or more microscopic holes formed by puncture by an electrical discharge.

In the lower end of the well III2 there is located a body of conducting liquid III-I on top of which is a layer of powdered carbon IiII-I. There is also located in the well III! a metal electrode rod IIII, the lower end of which extends into the layer of powdered carbon I I i-L In Fig. 15 there is shown a spark plug indicated generally by Illli which includes the improvements of the spark plug IIIII embodied in a construction which is otherwise conventional.

In Fig. 16 there is shown a spark plug indicated generally by I3I0 which is generally similar to the spark plug I2 I I), with certain exceptions. The spark plug IBI! includes an insulator body IIII with a bottom face ISIS- I and the insulator body I2II has formed therein a well I3I2 having a bottom wall ISH extending across the lower end of the well I3I2. 'I'he bottom wall I2 is spaced above the bottom face I3I9-I of the insulator body ISII, and in the lower end IIII of 8 the insulator body I2Ii there is formed a downwardly opening socket lill-2.

The spark plug Ille furthermore includes a metal ground shell Il on the lower end of which is a metal electrode tip |224 whose outer end extends into the socket ISIS- 3.

The embodiments of the present invention illustrated and described herein are by way of example and the scope of the present invention is not limited to the same or to the particular details thereof but is commensurate with any and all novel subject matter contained herein which may at any time properly under the patent laws be set forth in the claims hereof or originating herein, and the elements of any such claims are intended to include their functional or structural equivalents.

I claim:

l. In spark plug construction, an insulator body, the insulator body having formed therein a well with an open upper end and the insulator body including a bottom wall extending across the lower end of the well, electrode material in the well, the insulator body including a lower end having formed thereon external threads adapted for being screwed into an internally threaded opening in the wall oi' a combustion chamber, and a metal ground electrode on the lower end of the insulator body adjacent the bottom wall oi the well, the bottom wall of the well having one or :more metal wires embedded therein and extending therethrough.

2. In spark plug construction, an insulator body, the insulator body having formed therein a well with an open upper end and the insulator body including a bottom wall extending across the lower end of the well, electrode material in the well, the insulator body including a lower end having formed thereon external threads adapted for being screwed into an internally threaded opening in the Wall of a combustion chamber, and a metal ground electrode on the lower end of the insulator body adjacent the bottom wall of the well, the bottom wall of the well including a portion of conducting material extending therethrough.

3. In spark plug construction, an insulator body, the insulator body having formed therein a well with an open upper end, a bottom wall extending across the lower end o1' the well, electrode material in the well, the insulator body including a lower end having formed thereon external threads adapted for being screwed into an internal opening in the wall of a combustion chamber, and a metal ground electrode on the lower end of the insulator body adjacent the bottom wall of the well, the bottom wall of the well consisting entirely of a single mass of conducting material sintered to the insulator boch.

HAROLD R. FEICHTER.

BEFEBNCES CITED The following ref :t are of record in the ille o! this patent: 

